This invention relates to the manufacturing and assembly of movable sockets, for example, ball-joints as used in automotive steering and suspension systems, and more particularly, to a method and device for performing dual operations of closing one end of a movable socket without spinning, swaging, or welding, by means of an expanding cover-plate, and for setting a desired wear indicator distance between the surface of the expanding cover-plate and a pressure plate enclosed within the socket. While the invention is described in detail with respect to automotive applications, those skilled in the art will recognized the broader applicability of the invention.
Conventional ball-joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets comprise a housing having a circular cylindrical internal surface, a ball stud with a ball head contained in the housing, and a synthetic resin or sintered alloy bearing member supporting the ball head within the housing. These components are installed into the housing through a posterior opening, with the ball stud extending outward through an axially disposed anterior opening of a smaller diameter than the ball head. Traditionally, the posterior opening is closed by means of a cover-plate, spun, swaged, or welded in place. Once secured in place, the cover-plate presses on the bearing member either directly or indirectly through a resilient rubber intermediate component and a pressure plate.
Bearing components within the housing, against which the ball head or moveable component is articulated, perform best when the housing material is fully hardened, as it is better able to withstand the stresses and frictional wear associated with movement of the bearing components. Accordingly, the use of hardened materials greatly extends the useful life of the bearing components and the housing. However, hardened material surfaces greatly hinder traditional spinning, sagging, or welding operations required to enclose the housing. Therefore, as described in co-pending U.S. patent application Ser. No. 09/167,917, (herein incorporated by reference) a method and device for expanding a conical or convex cover-plate within the posterior opening is employed to secure and enclose the socket components within the socket housing, allowing for closure of a fully hardened housing without the need for traditional spinning, sagging, or welding operations.
Once assembled, movable sockets may be utilized as load carrying members in numerous mechanical systems, including automotive vehicle suspension and steering systems. Obviously, movable sockets or ball-joints employed in these applications are subjected to various operating conditions, and may be required to carry substantial loads. When wear develops, the performance of the movable socket or ball-joint degrades and, in the case of automotive applications, may result in erratic steering or excessive looseness and play in the vehicle suspension system.
As described in U.S. Pat. No. 4,070,121 to Graham, it is know to manufacture movable sockets and ball-joints with exposed wear indicators extending through the cover-plate so as to be in position to provide a visual indication of the wear condition of the ball-joint components. As the ball-joint components wear over time due to friction, the position of the exposed wear indicator shifts, corresponding to changes in the distance between the cover-plate and the inner components of the ball-joint. Traditionally, the distance between the outer surface of the cover-plate and the internal pressure plate of the ball-joint is utilized to determine the amount of wear experienced by the socket. To ensure an accurate wear indication, this distance is set, with a minimal part-to-part variation, to a predetermined tolerance by a secondary press or machining operation after the closure of the movable socket or ball-joint by the traditional spinning, swaging or welding operations.
Accordingly, it is highly advantageous to develop a ram device capable of both expanding a conical or convex cover-plate within a socket housing to enclose the housing without the need for specialized spinning, swaging, or welding operations, and for establishing the distance between the expanded cover-plate and the socket pressure plate at a predetermined reference for wear indication in a single machining operation.